It is often necessary to test production run parts on an on-going basis in order to assure quality standards have been met. When manufacturing plastic reflex parts, it is important to test the reflecting quality of the resulting part in order to make sure that it performs appropriately when installed in the vehicle. Traditionally, production run reflex parts were not tested on a regular basis because product samples would have to be sent to an off-site laboratory for testing. These off-site laboratories generally utilize a 100-foot long by 15-foot by 15-foot light tunnel that is located in a light-controlled chamber. Such conventional light tunnels require special equipment that is large in size and require skilled personnel to operate. These types of light-controlled testing chambers are costly to set up and maintain and require complete darkness to operate. Other problems with utilizing traditional light-tunnels is the unacceptable turn-around time in providing feedback information to the manufacturing facility. In some instances a factory could continue to make a defective tail lamp and not be aware that it was defective because the laboratory had not yet provided the test results back to the factory. This could result in defective parts being released to production which would be costly to correct.
Thus, it is desirable to provide a portable reflex comparator that allows a machine operator to test at her workstation the reflex performance of a newly molded part.
It is further preferred to provide a portable reflex comparator that allows a machine operator to quickly and easily test a newly run part, with little intervention in the daily production routine.
It is also preferred to provide a portable reflex comparator that allows various different reflex parts to be compared in order to assure they have met quality standards.
It is also desirable to provide a reflex comparator that is lightweight, inexpensive, easy for an operator to transfer from machine station to machine station, yet provides reliable information concerning the quality of a reflex part.
Another object of the invention would be to allow reflex parts to be tested in well-lit areas and to provide a machine that is not sensitive to ambient light.
According to one aspect of the present invention, the portable reflex comparator includes a laser light source, fiberoptic members to carry light to a focal point, and a collimating lens spaced apart from the focal plane. A meter with a gain control is provided for adjusting the signal output from a lock-in amplifier, with circuitry for processing signals from the laser light source and the reflex part being tested.
According to another aspect of the present invention, a method for testing a part having light reflecting characteristics is comprised of the step of first projecting a beam of laser light through a fan for chopping the laser light so as to modulate the beam of light to about 3000 hertz. Next, fiberoptics transmit two separate modulated signals emanating from the fan. One signal is an output signal which is directed to a focal plane. The second signal is a reference signal that is directed to a detector. The output signal emanates from the focal plane and diverges to a collimating lens spaced a predetermined distance from the focal point. A parallel beam of light then emanates from the collimating lens and is directed onto the surface of the reflex part. Initially, a model or standard reflex part is inserted in the testing device and is utilized as a “model” reflex part for comparing future production run parts to the model reflex part. A light signal is then emanated back from the reflex part, through the collimating lens where it converges to an input fiber located at the focal plane. The input fiber transmits the return signal to the detector where it is processed and sent to a lock-in amplifier. The purpose of the lock-in amplifier is to filter out all noise and light unless it is modulated at the preferred 3000 hertz reference signal. This is why the reference signal is transferred directly from the fan to the detector. By this means, the system is relatively insensitive to ambient light.
From the amplifier, a signal is transmitted to a meter to provide a visual output signal equal to X. A new reflex part to be tested can now be inserted into the comparator and the above steps are repeated. If the new reflex part has a value of greater than or equal to X, then the tested part is acceptable and it passes the test. Any value less than X means the part does not measure up to the part specifications and the machine operator will know that the injection molding machine is not creating parts to specification. When this occurs the machine can be recalibrated and then new parts are tested utilizing the aforementioned steps.